1. Field of the Invention
The present invention relates to a constant density recording (CDR) method used in hard disc drivers, and more particularly to a method of and a system for producing information for a CDR upon formatting a hard disc drive in a headerless manner by modifying ID fields and data fields.
2. Description of the Related Art
For hard disk drivers (HDD's), a headerless formatting method is known. The headless formatting method is a data recording method wherein data is recorded on an HDD using only data fields. In other words, no ID field is used in accordance with the headerless formatting method. In the case of HDD's utilizing a headerless format, CDR values should be used for a CDR. An example of such a headless formatting method is disclosed in Korean Patent Application No. 94-35785. In a conventinoal method, an ID field is used along with every data field upon reading and writing data. Positional information about data to be read or written is generated from each ID field. Such an ID field is used as an overhead for storing the positional information. They are not used as information for storing actual information for user data. This format is a headerless format. ID field signals are generated from a control unit other than that included in the HDD. For example, information such as cylinder numbers, head numbers and sector numbers are generated from the gray code unit for servo fields.
It is most efficient to obtain an increase in capacity of the disk of an HDD by having the disk store only data. In this case, however, it is additionally necessary to load positional information and CDR values. In order to satisfy such a requirement, a method is mainly used wherein a desired portion of an external buffer RAM is allocated in such a manner that a CDR value for every track is stored, as shown in FIG. 1. In accordance with this method, CDR values are stored in the buffer RAM. Subsequently, the CDR values and positional information are automatically loaded on corresponding sectors, respectively.
Loading of CDR values using the buffer RAM have been simply achieved using a method in which CDR values (for respective sectors of every track) loaded on a previous ID field are positionally shifted to the buffer RAM, thereby achieving an automatic loading thereof. In accordance with conventional methods, however, a split is generated in each servo-sector. Although data sectors, such as "CDRn" in FIG. 1, involving no split are inscribed with actual bytes of data, a data sector, such as "CDRn+2" in FIG. 1, involving a split can not be inscribed with actual bytes of data, as indicated by the shaded portions in FIG. 1. As a result, there is a waste of memory areas.
On the other hand, loading of CDR values from the buffer RAM is automatically carried out. There are five kinds of sources for accessing the buffer, namely, those for refresh, error correction, disk, host and main processor unit (MPU). In order to load all the CDR values, an additional buffer RAM should be used. Furthermore, the loading of CDR values should be carried out with a priority over the processing of other data values. This results in a burden to the buffer managing unit. Meanwhile, the HDD performs an error correction. As the error correction ability of the HDD increases, the quantity of data to be accessed per one sector increases correspondingly. As a result, the burden of the buffer managing unit increases even more.